* David Brown <david@xxxxxxxxxxxxxxx> wrote: > No, it's a hint - but one that gcc will take seriously and do its best > to honour (at -O0). The compiler cannot guarantee that it will be able > to put the data into a register - there are many things that could keep > it out of the register, including register pressure and the way the data > is used. The text says that with -O0 gcc will put all non-register > variables on the stack - that does /not/ imply that it will put all > register variables in registers. What does the ANSI C spec say about the "register" keyword ? Does GCC issue some warning when it fails to put such a variable directly into a register ? Is it that keyword still useful at all on todays compilers ? I'm not really experienced at that low level, but i can imagine scenarios where it's essential to keep certain things in registers (eg. when there's no valid stack), so the compiler should issue a warning (which can be made fatal w/ -Werror) in those cases. cu -- ---------------------------------------------------------------------- Enrico Weigelt, metux IT service -- http://www.metux.de/ phone: +49 36207 519931 email: weigelt@xxxxxxxx mobile: +49 151 27565287 icq: 210169427 skype: nekrad666 ---------------------------------------------------------------------- Embedded-Linux / Portierung / Opensource-QM / Verteilte Systeme ----------------------------------------------------------------------
